1. Technical Field
The present invention relates to the field of plant molecular biology. In particular, the invention pertains to cotton promoters and their uses in creating transgenic plants, and more specifically to cotton anther-specific promoters.
2. Description of the Background Art
Cotton is the most extensively used natural fiber in the textile industry. Annual production of cotton worldwide is over 100 million bales valued at 45 billion U.S. dollars. Although significant improvements have been made in quality and yield by means of classical breeding in the past decades, the potential for further improving the properties of cotton through classical breeding is limited due to requirements for species compatibility and available traits. Genetic engineering provides novel approaches for further improving cotton by introducing genes to create new germplasms with highly desirable characteristics, for example, insect pest resistance.
The anther is the male reproductive organ in flowering plants. Anther development can be divided into two general phases. During phase 1, most of specialized cells and tissues differentiate, microspore mother cells undergo meiosis and tetrads of microspores are formed. During phase 2, microspores are released from tetrads followed by pollen grain maturation, tissue degeneration, dehiscence and pollen release. Genes specifically expressed during anther and pollen development have been studied in a few plant species. Allen and Lonsdale, Plant J. 3:261–271, 1993; Bird, et al., Plant Mol. Biol. 11:651–662, 1988; Brown and Crouch, Plant Cell 2:263–274, 1990; Grierson et al., Nucl. Acids Res. 14:8595–8603, 1986; Hanson, et al., Plant Cell 1:173–179, 1989; Ursin et al., Plant Cell 1:727–736, 1989; John and Petersen, Plant Mol. Biol. 26(6):1989–1993, 1994; Atanassov et al., Plant Mol. Biol. 38:1169–1178 1998; Liu et al., Plant Mol. Biol. 33:291–300, 1997; Treacy et al., Plant Mol. Biol. 34:603–611, 1997; Agnes et al., Plant Mol. Biol. 40:857–872, 1999. Among the 20,000 to 25,000 expressed genes in tobacco anther, only 10,000 genes are anther-specific. Kamalay and Goldberg, Proc. Natl. Acad. Sci. USA 81:2801–2805, 1984; Koltunow, et al., Plant Cell 2:1201–1224, 1990.
A promoter is a DNA fragment which determines the temporal and spatial specificity of gene expression during plant and animal development. Many tissue-specific genes and their promoters have been identified and isolated from a wide variety of plants and animals over the past decade, including cotton tissue-specific genes and promoters. Loguerico et al., Mol. Gen. Genet. 261(4/5):660–671, 1999; Kawai et al., Plant Cell Physiol. 39(12):1380–1383, 1998; Song and Allen, Biochem. Biophys. Acta 1351(1):305–312, 1997; Ma et al, Biochim. Biophys. Acta 1344(2):111–114, 1997; John, Plant Mol. Biol. 30(2):297–306, 1996; Rinehart et al., Plant Physiol. 112(3):1331–1341, 1996; Hasenfratz et al., Plant Physiol. 108(4):1395–1404, 1995; John and Peterson, Plant Mol. Biol. 26(6): 1989–1993, 1994; John and Crow, Proc. Natl. Acad. Sci. USA 89(13):5769–5773, 1992. These plant tissue-specific promoters can be used to control the expression of foreign genes in transgenic plants in a tissue-specific manner that will dominate the majority of the second generation of transgenic crops. Some plant tissues do not express high levels of the transgene in all desired tissues or the particular desired tissue. In transgenic Bt cotton, for example, Bt gene expression level is extremely low in the flower, including in the anther, resulting in little protection from pest insects in these tissues. To achieve better control of pest insects of cotton, it would be highly advantageous to identify anther-specific promoters which can produce higher levels of gene expression in these tissues.